1. The Field of the Invention
The present invention relates generally to methods for performing kinematic analyses of environmental properties, and more particularly, but not necessarily entirely, to methods for detecting the speed and direction an object is traveling using conically scanned sensors.
2. Description of Related Art
It is often desirable to determine the motion characteristics of environmental features. For example, wind speed and direction are important to a number of disciplines, including scientific fields such as meteorology and atmospheric research as well as applied fields such as military and commercial travel. In these disciplines it is useful to have information regarding atmospheric wind speeds and directions, particularly at numerous and various points. However, it has often proven difficult to accurately, precisely and efficiently make such measurements.
Basic methods of wind speed and direction measurement include the use of balloons, and wind vanes or anemometers mounted on towers. Balloons may be used to approximate general wind speeds and directions based on their drift rates. The rate with which a wind vane rotates also indicates wind speed and the direction the vane points indicates wind direction. These methods are limited in that they only provide approximate wind speeds and directions for limited areas. The balloon only provides information regarding wind speeds and directions for that area over which it drifts and a vane for the location where it is fixed. Another limitation of the balloon and wind vane methods is the inability to gather information regarding wind speeds and directions at remote locations, particularly over the oceans where there are great expanses of water.
It is well known that the earth""s atmosphere is very complex and that wind speeds and directions may vary significantly at different altitudes within the same area, as well as varying from one area to the next. It would be an advantage to measure wind speeds and directions at a variety of altitudes, at numerous locations over a large area, and at remote locations which are difficult to reach. It would be a further advantage to make such measurements over a short period of time, in order to have a global understanding of the interrelationships of atmospheric conditions within limited windows of time.
Another technique for determining the wind velocity at an altitude, which overcomes some of the shortfalls of the known wind measurement procedures, uses a lidar system.
Lidar is an apparatus, similar in operation to radars, but having a transmitter which emits laser light instead of microwaves; lidar emits a laser beam which impinges upon an object and is backscattered, the backscattered light then enters into a receiver and is analyzed. Lidars have provided hope for a viable approach to the measurement of atmospheric wind speeds and directions because the backscattered light can provide information about the characteristic attributes of the object, such as distance, direction, or speed. The speed of the object has previously been determined from what is known as the Doppler shift in the frequency of backscattered light; that is, the speed of an object is determined from comparing the frequency of the light before and after it is backscattered, where the shift in the frequency of the light is a function of the speed of the object relative to the line of sight of the impinging light.
The direction of an object is determined from what is known as vector analysis; that is, the direction of an object is determined from comparing the velocity (or magnitude of the direction of movement) of an object from at least one point of reference, where at least two measurements of the object""s speed provides a resultant measurement of direction.
A problem in the art has been encountered in using lidar to gather information regarding small objects at great distances. It has proven difficult to produce lasers of a sufficiently narrow and clearly defined frequency so as to be able to clearly observe and evaluate frequency shifts in the backscattered light.
The prior art is thus characterized by several disadvantages that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
In view of the foregoing state of the art, it would be an advancement in the art to provide a method for kinematic analysis of conically scanned environmental properties which is simple to use. It would also be an advancement in the art to provide a method for kinematic analysis of environmental properties which does not require measurement of Doppler shifts in sensor signal frequencies. It would be a further advancement in the prior art to provide a method for kinematic analysis of environmental properties which allows measurement of wind speed and direction over a broad area, and throughout a vertical profile, and which can be used as a calibration and validation system for space based wind measurement systems.
It is therefore an object of the present invention to provide a method for kinematic analysis of conically scanned environmental properties which is simple to use.
It is another object of the present invention to provide such a method for kinematic analysis of environmental properties which does not require measurement of Doppler shifts in sensor signal frequencies.
It is a further object of the present invention, in accordance with one aspect thereof, to provide a method for kinematic analysis of environmental properties which allows measurement of wind speed and direction over a broad area, and which can be used as a calibration and validation system for space based wind measurement systems.
It is an additional object of the invention, in accordance with one aspect thereof, to provide a method for kinematic analysis of environmental properties which allows measurement of wind speed and direction throughout a vertical profile.
The above objects and others not specifically recited are realized in a specific illustrative embodiment of a method for determining the speed and direction a feature is traveling. The method preferably includes producing sensor signals, transmitted sequentially and not simultaneously, and projecting the sensor signals along straight lines lying on the surface of a conical shape. The conical surface is covered by continuous rotation of the transmission path, or by closely-spaced steps in time. The sensor signals may be in the form of lidar, radar or sonar for example. As the sensor signals are transmitted, the signals contact objects and are backscattered. The backscattered sensor signals are received to determine the location of objects as they pass through the transmission path. The speed and direction the object is moving may be calculated using the backscattered data. In one embodiment, the data may be plotted in a two dimensional array with a scan angle on one axis and a scan time on the other axis. The prominent curves in the plot of signal intensity may be matched with an arcosine curve, and analyzed to determine the speed and direction the object is traveling. The speed the object is traveling may also be determined by finding the slope of the arcosine curve at an inflection point. The direction of travel may also be determined by analyzing the extremes of the arcosine curve or the midpoints between inflection points. While the visual analysis of arcosine curves is a convenient embodiment of the kinematic conical analysis, wind speed and direction may also be determined by a non-visual mathematical analysis of the scan angle/scan time data array.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.